[unreadable] [unreadable] For many years now tamoxifen has been the endocrine treatment of choice for women with breast cancer. Despite the introduction of other SERMs and aromatase inhibitors, tamoxifen is still widely used and is expected to continue being widely used in important subgroups of breast cancer patients worldwide in the next decade. Many studies have consistently shown that long-term use of tamoxifen is associated with an increased risk of uterine corpus cancer. The association between duration of tamoxifen use and specific clinicopathological characteristics of subsequent uterine corpus cancers and ultimate survival is less clear and deserves further investigation in larger studies. In addition, knowledge on effect modification by recency of use, body mass index and hormonal replacement therapy is limited. Given the fact that the survival after uterine corpus cancer is generally good, individual studies lack statistical power to examine the effect of tamoxifen on uterine corpus cancer-specific survival. Pooling of data from previous studies will allow examination of cause- specific survival of patients with a uterine corpus cancer after tamoxifen with sufficient statistical power and is therefore of great importance. In addition, a combined dataset provides the opportunity to study the effect of tamoxifen in combination with other risk factors. This project involves pooled analyses of data from studies on tamoxifen and uterine corpus cancer. The specific aims of these analyses are: 1. To examine the association between duration of tamoxifen use and specific clinicopathological characteristics and survival of subsequent uterine corpus cancer; 2. To examine the precise nature of the duration-response curve for longer durations of tamoxifen use and effect modification by recency of use, weight and hormonal replacement therapy. From the studies on tamoxifen and uterine corpus cancer performed in recent years we selected the three largest published (100 cases or more) population-based case-control studies in which follow-up data (after uterine corpus cancer diagnosis, including cause of death), data on stage and histology of uterine corpus cancer as well as data on duration and recency of tamoxifen use, weight and use of hormonal replacement therapy were collected. Data from all patients with uterine corpus cancer after breast cancer in the three studies will be combined in one dataset, which will include about 1900 patients. Data from cases with matched controls in the three studies will be combined in a separate dataset, which will include about 1400 cases and 2600 controls. Data on grade and stage of the uterine corpus cancer were collected for part of the cases. For cases with missing data additional data will be collected and for part of the cases additional follow-up data (including cause of death) will also be collected. Cox regression and conditional logistic regression will be used for the analyses of the final combined datasets. [unreadable] [unreadable] [unreadable] [unreadable]